Choke mechanism



Jan. 26, 1965 c. R. GOODYEAR 3,167,254

cHoxE MEcHANIsM Filed Aug. 3l, 1962 2 Sheets-Sheet 1 A TTOR/VIYS .Jan- 26 1965 c. R. GOODYEAR 3,167,254

CHOKE MECHANISM Filed Aug. 3l, 1962 2 Sheets-Sheet 2 s e 4/ cnam/.fs A. Gooayf/M INVENTOR.

United States Patent O 3,167,254 CHOKE MECHANISM Charles R. Goodyear, Franklin, Mich., assigner to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Filed Aug. 31, 1962, Ser. No. 220,729 1 Claim. (Cl. 236-92) This invention relates to a choke mechanism for the charge forming device of an internal combustion engine.

When cranking a cold engine, the choke valve is maintained in a fully or nearly fully closed position either manually or automatically to provide a rich starting mixture. Once 4the engine fires, however, the choke valve should open slightly to permit suiilcient air ow for sustained engine operation. The choke valve is norinally opened automatically by engine suction. The engine suction is employed to open the valve either through direct actuation by the provision of an unbalanced choke valve or by having a separate suction motor that opens the choke valve. In many instances a combination of a suction motor and an unbalanced choke valve is utilized.

In previous choke mechanisms of the type having a vacuum motor to pull down or open the choke plate, the vacuum motor was directly coupled to the choke actuating mechanism. If a thermostatic spring positions the choke mechanism, the vacuum motor must overcome the tension in the thermostatic spring before pull down can be effected. This means that the degree of choke valve pull down is dependent upon the temperature induced preload in the thermostatic spring. The amount of pull down required is not dependent upon temperature,

however, and insuiicient choke valve pull down may result if extremely low temperatures are encountered.

It is, ltherefore, the principal object of this invention to provide an improved choke mechanism in which the amount of choke valve pull down is independent of the actuating means for the choke valve.

In an internal combustion engine charge forming device embodying this invention a choke valve is supported in the induction passage for movement from an opened to a closed position. Actuating means are operatively connected to the choke valve for moving the choke valve between the opened and closed positions. A suction motor is operatively connected to the choke valve to move the choke valve from a closed to a partially opened position in response to engine suction. The operative connection between the actuating means and the choke valve is constructed and arranged to provide for opening of the choke valve by the suction motor without atiecting the actuating means.

Further objects and advantages of this invention will become more apparent as this description proceeds particularly when considered in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a cross sectional view of a side elevation of a portion of an internal combustion engine charge forming device incorporating this invention.

FIGURE 2 is an end view, with portions shown in section, of the automatic choke actuating mechanism shown in FIGURE 1.

FIGURE 3 is a perspective View of the choke Valve and actuating mechanism shown in FIGURE l.

FIGURE 4 is a perspective view, in part similar to FIGURE 3, showing the parts in another position.

FIGURE 5 is a perspective view, in part similar to FIGURES 3 and 4, showing the parts in still another position.

Referring now in detail to the drawings, a portion of the charge forming device of an internal combustion engine is indicated generally at 11. The charge forming FPlee device 11 has an induction passage 12 and means for supplying fuel to the induction passage 12 (not shown).

A choke valve 13 is pivotally supported within the induction passage 12 by a choke valve shaft 14. The choke valve 13 is unbalanced, that is, it is eccentrically disposed relative to its pivot axis. The unbalance of the choke Valve 13 is such that the pressure differential created by a decrease in pressure in the intake manifold of the engine tends to rotate the choke valve 13 into an opened position.

A choke Valve actuating mechanism, indicated generally at 15, is provided to Irotatably position the choke valve 13 within the induction passage 12. The choke valve actuating mechanism 15 includes a choke housing 16 that is supported in a lixed position upon the charge forming device 11. A cover plate 17 is fixed to the choke housing 16 by bolts 18 and a clamp 19. A thermostatic spring 21 is contained within the choke housing 16 and has one end thereof affixed to the cover plate 17. The other end of the thermostatic spring 21 encircles a projecting end 22 of a lever 23. The lever 23 is rotatably supported upon a choke actuating shaft 24.

The choke -actuating shaft 24 is rotatably supported by the choke housing 16 and projects at one end therefrom. Secured to the other end of the choke actuating shaft 24 is a lever 25. The lever 25 has an inturned end 26 that projects through an aperture 27 formed in the lever 23. A torsional spring 28 encircles the choke actuating shaft 24 `and has one of its ends in abutment with the end 26 of the lever 25. The other end of the torsional spring 28 contacts a tang 29 formed upon the.

lever 23. Although the aperture 27 provides a lost motion connection with the end 26 of the lever 25, the torsional spring 28 normally causes the levers 23 and 25 to rotate together.

The projecting end of the choke actuating shaft 24 has secured thereto a lever 31. A lever 32 is aiiixed to the choke valve shaft 14. A link 33 is pivotally connected to the levers 31 and 32 to transmit motion from the choke actuating shaft 24 to the choke valve shaft 14 and choke valve 13.

A suction motor, indicated generally at 34, is provided to pull down or open the choke valve 13 slightly once the engine has started when the temperature is otherwise low enough for the thermostatic spring 21 to close the choke valve 13. The suction motor 34 comprises a cylindrical housing 35 formed integrally with the choke housing 16. Slidably supported within a bore 36 of the cylindrical housing 35 is a vacuum piston 37. Secured to and extending from the vacuum piston 37 is an actuating rod 38. Received in a longitudinal slot 39 formed in the actuating rod 38 is a downwardly extending projection 41 of the lever 25. A source of vacuum for actuating the vacuum piston 37 is provided by a conduit 42 that interconnects the bore 36 with a point in the induction system below the throttle valve of the charge forming device 11.

Operation Referring now to FIGURES 3-5, FIGURE 3 illustrates the choke valve 13 and the choke valve actuating mechanism 15 as they appear during cranking of the engine under low ambient temperatures. The thermostatic spring 21 has rotated the lever 23 in a counterclockwise direction. The movement of the lever 23 was transmitted through the torsional spring 28 into counterclockwise rotation of the lever 25. The choke actuating shaft 24 and lever 31 were thus rotated in a counterclockwise direction pulling the link 33 downwardly to rotate the choke valve shaft 14 and choke valve 13 into the closed position. If the temperature of the bimetal were sufficiently low, the lever 23 would be rotated until it abutted a stop 42 formed integrallywith ,the chokehous-r ing 16.

During cranking of the engine a pressure differential is mean that thedegr'ee of 4choke ,valve pulldown would,

, be dependent upon the temperature of the thermostatic l `spring, 21; If the suctionlmotor was created that `exerts atorce. tending toopen the choke.,`

valve 13. The tension in thetorsion spring 28'and the:

thermostatic spring 21 resist opening Vof thek choke, valve 13, however. mediate and substantial decrease in pressure in the induction system belowthe throttle valve of theV charge form'- ing device 11. This, decrease in pressure'will be transrnittedthrough the conduit 42 to the suction motor 34.v

The pressure differential across theA vacuum piston 37 Y will cause theV vacuum piston 37 to move into the bore 36. This causes the lend of the slot 39 in the actuating rod 38 to contact the projection 41 ofthe lever 2,5 and rotate the lever 25, the choke actuating shaft 24, andthe lever 31 in aVV clockwise direction.

valve 13 in a clockwise direction.V The choke valve 13- is thus-opened slightly to permit sufficient lair. flow for smooth engine operation. :The offset orunbalance of the choke valve 13. also assists in its opening.

RotationY of `thechokev actuating shaft 24 by the suc- Y Once theY enginefires there will be an im-v K Y This moves the, link 33 upwardly to rotate vthe choke valve shaft 14and choke vtemperature of the thermostatic would be linsuiicient pull down when the temperadesigned to provide a certain degree vof,v pull down at a given spring 21, there fout departing ,fromVr the .spirit and. scope Y of kthe invention as delinedby theappended'claim..

I claim:Vv Y n i Y A ,charge forming. device for an internal combustion engine comprising an induction passage, a chokevalve e positioned` in` said induction passageafor controlling. the

tion motor 34 is accomplished without affecting the .posif Y tion of the lever. 23 as long'as the torque .exerted by the` thermostatic spring 21 exceedsthetorque exerted .upon Y thetorsion spring 28v by the unbalanced choke valve 13gl andthe suction motor 34; VWhen-.thiscondition prevails,

Vthe torsion spring 28 will yieldA toallow thelever v25[0v rotate with respect to the. lever Z3 (FIGURE 4)'. vThe.`

amount of'relativerotation is limited by the lWidth lof the aperture`27' formed inthe lever 23.

The thermostatic springv 21,5is heated-in response totV engine temperature by an exhaust manifoldA stoveorrinf some vother rknown manner. "When heated, the tension inthe thermostatic spring'21 decreases to rotate the lever"- 23 Yin aclockwise direction (FIGURE 5). Rotationof.; the ilever 23,;in the clockwise direction isgtransmitted:y

through the torsionnspringZS to the choke actuating shaft 24 when the rotational effect exerted bythe torsion spring` flow of rair therethrough, anautomatic choke actuating Y mechanism comprising arhousing, a choke valve actuating^1 shaftjournaledf withinsaid. housing,nlinkage means voperatively connecting said choke valve actuatingshaft with said choke-valve, a .first lever supportedrwi'rhin saidhousing, and fixed Atosaidchoke valve. actuating shaft, a second lever Vsupportedwithin saidv housing and, journaled uponsaid chokev valve yactuatingshaft, meansI providinga lost motion connection between said levers, springmeans.

' operatively` connected to' saidvlevers ,for resisting relative rotation54 between said-levers, aV suction" motorn operativelyc onnectedrtov saidrst lever, and-thermally responsivel means havingl Oneend-thereof operatively connected to saidsecond'leven-to rotate saidk secondvlever in-res ponse n. to temperature variations, :said `spring-jrneans being yieldexceeds therrotationaleiect caused by the Y,suction motor 34. 'As theftemperature of the engine raises further, the; position ofthe choke Valvefbecomes dependent-solely upon the temperature, of the thermostatic` spring `21 in conjunction with the rotationalelfect exerted upon the.

choke `valve 13y by Y its unbalance.

able upon actuationV of ,saidfsuctionmotor for relative` rotation between said levers to loperate said` choke -valve Without affecting the positionfotsaid secondv lever and saidv i -therrnallyjresponsive means. Y f' It should be readily apparent thatif the lever 23 were' afiixed to the ychoke actuating shaft 24,- as has. been heretofore common, the suction motor 34 vwould have -to overcome the tensionin thethermostatic springrZlrbefore choke valve. pull down could be effected. This would g y v References:v Cited inthe yfile. ofthis. patent l Y Y ,l UNITED STATES PATENTS" 2,381,751 *Y [Hunt Aug. 7, 1945 I 2,818,238 Y Olson Dec. 31,1957y 2,834,586 rSzwarvgl/Jlski May 13; 1958 2,998,233 Marse'e Aug. 29, 1961 Y 3,006,617fy Moseley Oct. 31,' 1961 

